1. T:Toxicology&
ChemicalFoodSafety
Iodide Residues in Milk Vary between
Iodine-Based Teat Disinfectants
Elizabeth A. French, Motoko Mukai, Michael Zurakowski, Bradley Rauch, Gloria Gioia, Joseph R. Hillebrandt, Mark Henderson,
Ynte H. Schukken, and Thomas C. Hemling
Abstract: Majority of iodine found in dairy milk comes from the diet and teat disinfection products used during
milking process. The objective of this study was to evaluate the effects of 4 iodine-based teat dips on milk iodide
concentrations varying in iodine level (0.25% vs. 0.5%, w/w), normal low viscosity dip versus barrier dip, and application
method (dip vs. spray) to ensure safe iodine levels in dairy milk when these products are used. The iodine exposure
study was performed during a 2-wk period. The trial farm was purged of all iodine-based disinfection products for 21
d during a prestudy “washout period,” which resulted in baseline milk iodide range of 145 to 182 ppb. During the
experiment, iodine-based teat dips were used as post-milking teat disinfectants and compared to a non-iodine control
disinfectant. Milk iodide residue levels for each treatment was evaluated from composited group samples. Introduction of
different iodine-based teat disinfectants increased iodide residue content in milk relative to the control by between 8 and
29 µg/L when averaged across the full trial period. However, residues levels for any treatment remained well below the
consumable limit of 500 µg/L. The 0.5% iodine disinfectant increased milk iodide levels by 20 µg/L more compared
to the 0.25% iodine. Compared to dip-cup application, spray application significantly increased milk iodide residue by
21 µg/L and utilized approximately 23% more teat dip. This carefully controlled study demonstrated an increase in milk
iodide concentrations from iodine disinfectants, but increases were small and within acceptable limits.
Keywords: iodine, milk, residue
Practical Application: Dairy products contain iodine from the cow’s diet and teat disinfectants used in the milking
process. Milk iodine was compared between teat disinfectants varying in iodine concentrations to a disinfectant without
iodine. As iodine in teat disinfectant increased, so did the iodine residues in milk. Throughout the 2-wk testing period,
milk iodine remained at levels acceptable for human consumption.
Introduction
Iodine is crucial to human health both as an essential dietary
element necessary for proper thyroid function (WHO 2004) and
as a germicide important in the reduction of bacterial popula-
tions, particularly as pre- or post-milking teat disinfectant (Galton
2004; Ceballos-Marquez and others 2013). Although iodine de-
ficiency poses health risks and remains problematic in many parts
of the world, over-dosage of iodine is also associated with health
risks, such as toxic goiter, hyper-thyroidism, and hypo-thyroidism
(Delange and others 1999; WHO 2004; Medici and others 2014;
Sun and others 2014; Shi and others 2015). The Recommended
Daily Allowance for iodine consumption in healthy adults is 150
µg. Daily dietary intake of iodine levels greater than 1100 µg
(tolerable upper level, UL) may result in thyroid dysfunction. In
addition to iodized table salt, dairy products have been cited as a
major source of dietary iodine in most developed societies (WHO
MS 20152042 Submitted 12/8/2015, Accepted 5/6/2016. Authors French, Hen-
derson, and Hemling are with DeLaval Manufacturing, 11100 N. Congress Drive,
Kansas City, MO, 64153, U.S.A. Author Mukai is with Dept. of Food Science,
Cornell Univ, Stocking Hall, 411 Tower Rd., Ithaca, NY, 14853, U.S.A. Authors
Mukai, Zurakowski, Rauch, Gioia, Hillebrandt, and Schukken are with Cornell
Univ., Ithaca, NY, 14853, U.S.A. Author Gioia is with Quality Milk Produc-
tion Services, 240 Farrier Rd., Ithaca, NY, 14853, U.S.A. Author Hillebrandt
is with Animal Health Diagnostic Center, 602 Tower Rd., Ithaca, NY, 14853,
U.S.A. Author Schukken is with GD Animal Health, Arnsbergstraat 7, P.O. Box
9, 7400, AA Deventer, the Netherlands. Direct inquiries to author French (E-mail:
Lizzy.French@delaval.com).
2004; Norouzian and others 2009). The iodine level in dairy
products can vary widely depending on the level of iodine in soil
and vegetation consumed by dairy cattle (Berg 1985; Borucki and
others 2010).
Upon contact with milk, the germicidal iodine is converted
to nongermicidal iodide. In cow milk, and in drinking-water,
most iodine exists in the form of soluble iodide (Sanchez and
Szpunar 1999; WHO 2003, 2004). Therefore, soluble iodide in-
stead of total iodine concentrations are usually measured in cow
milk (Melicherik and others 2006). In many countries, milk io-
dide levels less than 500 µg/L are considered acceptable for human
consumption (WHO 2004). As milk levels of iodide fluctuate con-
siderably, both within and between farms, there have been renewed
concerns that use of iodine-based pre-milking and post-milking
teat disinfectants significantly contribute to high or too high levels
of iodide level in milk (Borucki Castro and others 2010, 2012).
The objective of this study was to evaluate the impact of 2 con-
centrations and 2 application methods of iodine disinfectants on
milk iodide residues. All iodine-based treatments were compared
with a non-iodine–based control product to control for baseline
levels of iodine.
Materials and Methods
Animal selection and identification
One-hundred healthy Holstein or Holstein-cross dairy cat-
tle were enrolled in the study. All animals participating in the
study were required to have 4 functional quarters free of major
C 2016 Institute of Food Technologists R
T1864 Journal of Food Science r Vol. 81, Nr. 7, 2016 doi: 10.1111/1750-3841.13358
Further reproduction without permission is prohibited

2. T:Toxicology&
ChemicalFoodSafety
Iodine teat disinfectants and milk iodide levels . . .
intramammary mastitis pathogens (Staphylococcus aureus, Streptococ-
cus organisms, and coliform organisms) based on bacteriological
analysis of aseptically collected quarter-level milk samples on day
−28 (NMC 1999). All enrolled animals had good teat end con-
dition based on a teat end scores of less than 3.0 out of 5 (Nei-
jenhuis and others 2001). Animals that developed mastitis dur-
ing the course of the treatment period were excluded from final
analysis. The cow composite cell count of all animals was below
200000 cells/mL at the start of the study. Daily management,
housing, and nutrition for the treatment groups was identical.
All cows were fed the same fresh TMR 3 times a day after each
milking and fresh drinking water was provided ad libitum. Known
iodide binders, such as cottonseed meal, were not used during the
trial. All study animals were housed in a free-stall facility, and were
milked 3 times per day in a double 10 parlor at approximately 4
a.m., 12 p.m., and 8 p.m. Approximately a month before the iodine
washout period, milk iodide concentrations were measured from
12 individual cows from the herd, which measured as 228.1 ± 2.0
ppb. Milking procedures included dry wipe, stripping, and unit
attachment. All animals were checked 3 times a day by pre-milking
stripping for clinical signs of mastitis.
Treatment group assignments and application. One-
hundred cows enrolled in the study were divided into 5 treatment
groups with 20 animals per group. Treatment groups are described
in more detail in Table 1. Each animal was assigned to treatment
groups, including a non-iodine control (CTL), a 0.25% iodine
post-dip, sprayable, or barrier dip (0.25 DIP; 0.25SP; 0.25BAR),
or a 0.5% iodine post-dip (0.5DIP; Table 1). Groups were bal-
anced with regard to lactation number, lactation stage, milk yield,
and teat end condition.
Products were applied by manually dipping the teat of each
quarter of each enrolled cow according to the group designations
CTL, 0.25DIP, 0.50DIP, and 0.25BAR with the indicated prod-
uct. For cows enrolled in groups CTL, 0.25DIP, 0.50DIP, and
0.25BAR, a nonreturn dipper cup was utilized for application of
teat dip. Cows in group 0.25SP were manually sprayed using a
710 mL upward trigger sprayer (see also Table 1). Teat dip cover-
age for all treatment groups was required to cover at least 75% of
the teat extending from the teat-end toward the base of the teat.
Study design
Washout period (days −21 to 0). Prior to the washout pe-
riod, 1% iodine was used for both pre- and post-milking teat
disinfection. During prestudy days −21 to 0, all iodine-based
products including teat dip and salt blocks were removed from
the study farm. Pre-milking, all quarters were dipped with a non-
iodine, lactic acid-based product (BiofoamTM
, DeLaval, Kansas
City, Mich., U.S.A.) and post-milking, quarters were dipped with
a peroxide-based dip (PrimaR
, DeLaval). The farm did not use
any iodine-based pipeline sanitizer or back flush.
On days −21 and −14 bulk tank milk sample were collected and
on days −7 and 0 composite cow milk samples were collected for
iodide concentration measurement during the afternoon milking
from all cows eligible for enrollment in the study. A more detailed
description of milk sampling for days −7 and 0 is provided below.
On the last day of washout period (day 0), cows were assigned to
treatment groups to achieve a balanced design to 1 of 5 treatment
groups as described above.
Treatment period (study days 1 to 14). Each group, CTL,
0.25DIP, 0.25SP, 0.5DIP, and 0.25BAR (Table 1), were assigned
a unique color that corresponded to a colored dipper cup and
leg band. All cows were dipped pre-milking with a non-iodine,
lactic acid–based product. Immediately post-milking, cows from
groups CTL, 0.25DIP, 0.5DIP, and 0.25BAR were post-dipped
by trained farm staff, using the respective teat disinfectant in the
corresponding colored dipper cup. Cows in group 0.25SP were
sprayed with the corresponding teat disinfectant using a manual
trigger sprayer bottle (24-oz., 710 mL, M21000X, Coburn Co.,
Inc., Whitewater, Wis., U.S.A.). Animals in 0.25SP had colored
leg bands that corresponded to the colored manual trigger spray
bottle. The study director was present at each milking during the
treatment period study days 1 to 14 to monitor correct application
and allocation of teat dip products. However, personnel applying
the disinfecting products and performing the analysis were blinded
to all the treatment groups. All study animals remained in the same
treatment groups from days 1 to 14 of the experimental period.
Sample collection and iodide analysis
Collection of total mixed ration samples. On days −21
and 14, a sample of the total mixed ration (TMR) being fed to all
animals was collected for determination of the iodine concentra-
tion. The TMR sample was collected from freshly mixed rations.
A total of 12 to 20 subsamples of the mix were collected from
different locations in the feed bunk. All subsamples were mixed
well in a clean plastic bag to form a composite sample of approxi-
mately 1 kg. The composite sample was divided in half and 0.5 kg
was submitted to the laboratory for total iodine level evaluation
by inductively coupled plasma mass spectrometry (ICP-MS) at the
Diagnostic Center for Population and Animal Health (DCPAH)
at Michigan State Univ., Lansing, Michigan, U.S.A.
Collection of water samples. On days −21 and 14, a sam-
ple of the drinking water that was available to all experimental
animals was collected for measurement of iodide concentration. A
200 mL sample of clean water was collected from the water line
entering the dairy facility to prevent cross contamination of water
by feed or other on-farm sources. Samples were submitted to the
Cornell Animal Health Diagnostic Center (AHDC) Toxicology
Laboratory (Ithaca, N.Y., U.S.A.) and analyzed.
Collection of milk samples for determination of iodide
content. During the washout period, bulk tank milk samples
were collected on days −21 and −14 and individual composite
cow samples consisting of milk from all 4 quarters were collected
on days −7 and 0. A composite cow sample of approximately
100 mL was collected from each cow eligible to participate in
the trial via an Electronic Milk Meter (Tru-Test Inc., Mineral
Wells, Tex., U.S.A.) sampling device. To avoid cross contamination
during collection of milk samples with iodine from the dipper
cups, research staff collected all milk samples whereas teat dip
application was performed by farm personnel. After each sample
was collected, the barrel of the sampling device was soaked and
rinsed with fresh facility water and then allowed to drain before
sampling the next animals.
Milk samples were immediately chilled and transported to a
laboratory facility where they were prepared for shipping. A 10 mL
aliquot from each composite milk sample of all cows in the same
treatment group was placed in each of 3 separate vials to create 3
pooled replicate samples. A volume of 200 mL from these replicate
pooled samples was then sent to the Cornell AHDC Toxicology
Laboratory for analysis of iodide content (Ithaca, N.Y., U.S.A.).
A total of 6 (3 on day −7 and 3 on day 0) pooled samples were
evaluated for iodide content during the pretrial period. All pooled
samples were evaluated within 14 d after collection. A pilot study
done in the lab showed no changes in iodide concentration when
samples are stored in 4 °C for up to 14 d.
Vol. 81, Nr. 7, 2016 r Journal of Food Science T1865

3. T:Toxicology&
ChemicalFoodSafety
Iodine teat disinfectants and milk iodide levels . . .
Table 1–Test products and application procedure in the 5 treatment groups.
Treatmenta
Item CTL 0.25DIP 0.25SP 0.50DIP 0.25BAR
Application Method Dip Dip Spray Dip Dip
DeLaval trade name PrimaTM TriFenderTM TriFenderTM BovidipTM IodofenceTM
Presentation Liquid Liquid Liquid Liquid Liquid
Dose RTUb RTU RTU Concentrate to be diluted 1+3 RTU
Active ingredient Hydrogen peroxide Iodine Iodine Iodine Iodine
Concentration of Active (%) 0.5 0.25 0.25 0.5 0.25
Total iodinec in RTU product None 4100 ppm 4100 ppm 7200 ppm 4100 ppm
a
Treatments: Non-iodine control (CTL); 0.25% iodine post-dip, sprayable, or barrier dip (0.25 DIP; 0.25SP; 0.25BAR); or 0.5 % iodine post-dip (0.5DIP).
b
RTU, ready to use.
c
Total iodine = sum of iodine from all ingredients, including non-active ingredients.
During the treatment period, milk weights were recorded for
all animals and individual cow milk samples were collected from
each cow for iodide concentration evaluation on study days 1, 4, 7,
and 10 during the afternoon milking using a Thru-Test Electronic
Milk Meter. Milk samples collected on day 14 were collected
during the morning milking due to an approaching inclement
weather event (Hurricane Sandy).
Within each treatment group of 20 cows, a 10 mL aliquot from
each composite sample was placed in each of 3 separate vials to
create 3 pooled replicate samples. The 3 well-mixed separate vials
consisted of a 200 mL pool of 20 cows within a treatment group.
Five individual cows in the CTL group were evaluated through-
out the study for iodide content to determine the variability in
individual cow samples. Total of 75 pooled samples were sent to
the Cornell AHDC Toxicology Laboratory for analysis of soluble
iodide content.
Iodide analytical procedure. Milk samples were analyzed
for soluble iodide content at the Cornell AHDC Toxicology Lab-
oratory by ion selective electrode (ISE) method (with slight mod-
ification to AOAC official method 992.24; AOAC 2006). Briefly,
a 20 mL milk sample was transferred into a 50 mL polypropy-
lene centrifuge tube and deproteinated with 4 mL of 3% (v/v)
acetic acid under a mechanical shaker for 20 min. Samples were
then centrifuged at 2000 rpm for 10 min and the aqueous phase
was filtered and transferred to a clean plastic container. The ionic
strength of the solution (25 mL of filtrate) was adjusted by adding
0.5 mL of 5M sodium nitrate, followed by adding 0.25 mL of
25% (v/v) nitric acid solution prior to measurement of soluble io-
dide using a solid-state combination-specific ion electrode (Orion
9653BNWP, Thermo Fisher Scientific, Waltham, Mass., U.S.A.).
Water samples were analyzed directly without the extraction step.
A linear standard curve (R2
> 0.99) was generated in every
assay using a certified reference material of iodide (41271, Sigma-
Aldrich, St. Louis, Mo., U.S.A.), which is traceable to NIST certi-
fied reference materials. Extraction efficiency was evaluated along
with each assay by spiking a known amount of reference material
(500 parts per billion (ppb); mid-range of the generated standard
curve) to the reference milk before the procedure and calculating
the recovery. Percent recovery was 84.6 ± 2.6%, intra- and in-
terassay coefficient of variability (CV) was within 1%. All results
are expressed as micrograms per liter (µg/L), which is equivalent
to parts per billion.
Total iodine analysis in TMR followed the method of Wahlen
and others (2005) using an Agilent 7500ce ICP/MS (Agilent,
Santa Clara, Calif., U.S.A.). Briefly, the sample was diluted 20-
fold with a solution containing 0.5% EDTA and Triton X-100,
1% ammonium hydroxide, 2% propanol, and 20 µg/L of scan-
dium, rhodium, indium, and bismuth as internal standards. The
ICP/MS was tuned to yield a minimum of 7500 cps sensitivity for
1 µg/L yttrium (mass 89), less than 1.0% oxide level as determined
by the 156/140 mass ratio and less than 2.0% double charged
ions as determined by the 70/140 mass ratio. Concentration was
calibrated using a 4-point linear curve of the iodine-to-internal
standard (SpecpureR
, Alfa Aesar, Ward Hill, Mass., U.S.A.) re-
sponse ratio. The lowest iodine concentration of the standard curve
was 1 ppb (µg/L). An Natl. Inst. of Standards and Technology
(NIST, Gaithersburg, Md., U.S.A.) urine iodine standard reference
material was used as a control.
Statistical analyses
Data were entered into a database and checked for accuracy.
Descriptive statistics were used to describe the distributions present
in the data and to check for outliers. Because samples were taken on
the same animals over time, a repeated measures linear regression
model was used to estimate iodide residue concentrations in milk
for each period. The linear model used was:
Milk iodide = Time + milk production + treatment
+ replicate + error
where time was the study day of collection of the milk sample
(study days −7, 0, 1, 4, 7, 10, 14), milk production was the
daily milk production per day, treatment was the particular teat
disinfectant, replicate was an indicator variable for cow, and error
was a normally distributed random error. The replicate term was
used to correct for the repeated measurement nature of the data.
Two-way interactions of variables in the model were evaluated.
Least square means of the interaction term of time × treatment
were calculated to estimate mean iodide levels in milk per sampling
time during the treatment period. Regression models were per-
formed to determine the effect of the application method (spray
versus dip) by comparing treatments 0.25DIP and 0.25SP. Regres-
sion models were also run evaluating iodine concentrations in the
dip were compared in the dip on milk iodide concentrations was
performed by comparing 0.25% iodine disinfectant versus 0.50%.
Significance testing of the treatment groups was performed with
statistical significance declared at P < 0.05.
Quality assurance
The trial was conducted under GLP and GCP standards. Quality
Assurance was performed by an independent quality assurance unit
at Cornell Univ.
T1866 Journal of Food Science r Vol. 81, Nr. 7, 2016

4. T:Toxicology&
ChemicalFoodSafety
Iodine teat disinfectants and milk iodide levels . . .
Table 2–Least square means of treatment milk iodine across the full trial period (days 0 to 14) and contributiong of iodine teat
dips to milk iodine relative to the control.
Treatmenta
Parameter CTL 0.25DIP 0.25 SP 0.50DIP 0.25BAR SEM
Milk Iodide 148 157 178 177 163 5
Contribution to milk iodine – 8 29 29 15 7
a
Treatments: Non-iodine control (CTL); 0.25% iodine post-dip, sprayable, or barrier dip (0.25 DIP; 0.25SP; 0.25BAR); or 0.5% iodine post-dip (0.5DIP).
Results
Total mixed ration iodine concentration
Iodine concentration of the TMR fed to all study animals was
evaluated during the washout period (day −21) and at the end of
the treatment period (day 14). Iodine concentration in the TMR
on days −21 and 14 was 2310 and 1900 µg/kg dry matter (DM),
respectively.
Water iodide concentration
Iodide concentration of the drinking water available to all study
animals were determined on days −21 and 14. Water soluble iodide
levels decreased from 4.54 to 2.72 µg/L between the washout and
the treatment period.
Milk iodide concentration
Washout period. No significant relationship between treat-
ment group and either days in milk, lactation number, milk yield,
or teat end score were observed before the start of the treatment
period (P > 0.1). After use of a 1% iodine, pre- and post-milking
teat disinfectant was ceased on study day −22, milk iodine levels
decreased significantly from 228.1 ± 2 µg/L and almost immedi-
ately stabilized at 165 ± 2 µg/L on days −21 to −7 in bulk tank.
A slight 3 µg/L decline in milk iodide occurred between prestudy
days −14 and −7.
Treatment period. On days 1, 4, 7, 10, pooled milk io-
dide levels for all treatments were consistently around 150 µg/L
(Table 3). On day 14, milk iodide levels increased by approx-
imately 50 to 100 µg/L. The CTL animals similarly increased
(P < 0.05) in milk iodide on day 14 by 48 µg/L compared to day
10. Throughout the study period, milk yield decreased (P < 0.05)
over the study across all treatment groups (Table 4). Compared to
the control, 0.25BAR had lower (P < 0.05) daily average milk
yield.
Least square means of treatments revealed that all treatments
aside from 0.25DIP were higher (P < 0.05) in milk iodide than the
CTL, peroxide-based control disinfectant (Table 2). The treatment
and study day interaction revealed a number of study days with
different (P < 0.05) milk iodide values compared to other days.
The least square means of treatment within study day are presented
in Figure 1. To evaluate the variability in individual cow samples,
we also evaluated the samples of individual CTL for iodide content
(Table 5). Within cow sample averages varied from 97 to 169 µg/L
whereas standard deviations ranged from 9 to 29 µg/L.
Increasing iodine concentration in the teat disinfectant from
0.25% to 0.5% increased (P < 0.05) milk iodide residues by 20 ±
7 µg/L. The same product (TriFenderTM
) was used for 0.25DIP
and 0.25SP group except different application methods were used,
by dipper cup and sprayer, respectively. Regression analysis com-
paring spraying 0.25SP versus dipping 0.25DIP resulted in 21 ±
6 µg/L greater (P < 0.05) milk iodide (Table 3).
Discussion
The objective of this study was to evaluate the potential increase
in iodide residues in milk from iodine containing post-milking teat
disinfectants with differing iodine concentration, viscosity, or ap-
plication method. In addition, the impact of these treatments were
investigated over a 14 d time period. The iodine levels measured
in the diet and water in the current study were within the ac-
ceptable (diet during pretreatment period was slightly higher than
NRC requirement) and average range and baseline milk concen-
tration reflected a typical milk iodine level in the U.S. Adequate
concentrations of total iodine in cattle diet are considered to be
500 to 2000 µg/kg DM for cattle with 450 µg/kg DM as min-
imum NRC requirements level for lactating cows (NRC 2001).
Water was also within recommended levels. Iodine occurs natu-
rally in water predominately in the form of iodide. Average water
concentration of iodide in drinking water in the United States is
4 µg/L, with observed maximum values as high as 18 µg/L (WHO
2004).
There was a decline (P < 0.05) of iodide levels during the wash-
out phase. This result is similar to that found by Galton and others
(2004), who determined that after discontinuing the use of 0.5%
post-milking teat disinfectant, milk iodine decreased immediately
from 27.0 to 31.8 µg/L. When pre- and post-milking iodine teat
disinfectants varying in concentration of iodine from 0.25% to
0.5% were discontinued, milk iodide levels immediately decreased
(Rasmussen and others 1991). As expected, we observed increases
in milk iodide concentrations when using iodine teat disinfectants
compared to a non-iodine disinfectant (Figure 1), suggesting io-
dide absorption through the teat skin and canal that enters into
the milk, elevating milk iodide as suggested previously (Scheybal
and others 1980; Aumount 1987). The increase in milk iodide
concentrations was relatively small in all groups of disinfectants
and all concentrations measured were certainly well below the
WHO maximum guideline of 500 µg/L. The maximum increase
above baseline of approximately 100 µg/L was observed on day
14 of the study. Results from this study are in line with the review
by Flachowsky and others (2014), noting increases in milk up to
100 µg/L when iodine teat disinfectants were introduced.
The increase in milk iodide levels during 14 d of treatment
indicate that the use of different types of iodine teat disinfec-
tants do contribute to increase of iodide residues, but all levels
remained consistently below 500 µg/L (Table 2). Teat disinfec-
tant contribution to milk iodide levels ranged from 8 to 29 µg/L
based on averages across the entire treatment period. Compared
to the 0.25% iodine teat dip, 0.5% iodine teat dip increased milk
iodide levels by a modest 20 µg/L, indicating an impact of iodine
concentration in the disinfectant on iodide residues.
Generally, some variation occurred in iodide concentrations
throughout the 14 d in the study (Table 3 and Figure 1). An in-
crease in iodide concentration was observed on day 14 of the study
across all treatments including the control where no iodine teat
disinfection was used. Few studies have looked at treatment effects
Vol. 81, Nr. 7, 2016 r Journal of Food Science T1867

5. T:Toxicology&
ChemicalFoodSafety
Iodine teat disinfectants and milk iodide levels . . .
Table 3–Least squares means of treatment milk iodide (µg/L) in pooled cow milk samples across experimental study days compared
to a non-iodine control.
Treatmenta
Study Day CTL 0.25DIP 0.25SP 0.5DIP 0.25BAR SEMb
Iodide (µg/L – ppb)
1 171a 148a 172a 136a 164a 8
4 116b 128a 154a 160a 144a 8
7 140a 137a 150a 157a 135a 8
10 132b 150a,b 154a 155a 133b 8
14 183b 221a 258a 277a 240a 8
Inline alphabets (a,b) within a row compare control (CTL) to other treatments within study day.
a
Treatments: Non-iodine control (CTL); 0.25% iodine post-dip, sprayable, or barrier dip (0.25 DIP; 0.25SP; 0.25BAR); or 0.5% iodine post-dip (0.5DIP).
b
SEM, standard error of the mean.
Table 4–Least square means of treatment milk yields (kg) across washout period and experimental study days.
Treatmenta
Study day CTL 0.25DIP 0.25SP 0.5DIP 0.25BAR SEMb
Milk yield (kg)
−21 42.6 43.5 39.8 41.6 37.9 2.6
−14 41.4 43.8 38.3 40.6 36.4 2.6
−7 39.9 41.7 36.7 38.2 34.2 2.6
0 38.1 40.7 36.5 36.4 35.0 2.6
1 40.2 42.1 37.4 37.7 36.7 2.6
4 38.5 41.0 36.1 35.8 35.0 2.6
7 37.7 39.6 35.4 36.2 33.9 2.6
10 37.9 39.7 36.0 36.0 34.5 2.6
14 34.6 38.2 34.3 34.1 32.8 2.6
a
Treatments: Non-iodine control (CTL); 0.25% iodine post-dip, sprayable, or barrier dip (0.25 DIP; 0.25SP; 0.25BAR); or 0.5% iodine post-dip (0.5DIP).
b
SEM, standard error of the mean.
with data reported over time. Galton (1984) looked at treatment
over time and demonstrated that the iodine teat disinfection in-
creased milk residues on day 1 after starting treatment and resulting
increase was remained constant over the 8 d study period. Many
studies were conducted over similar or longer treatment time,
but only single values for whole treatment period are typically re-
ported. Because of the threat of Hurricane Sandy associated-power
outage, in this study the day 14 milk samples were collected in
the morning instead of regular afternoon milking, 8 h earlier than
usual. With the approaching hurricane, environmental weather
conditions were quite different compared to previous study days.
Based on local weather, barometric pressure rapidly dropped from
a study period average of 29.96 to 29.38 mm Hg, wind gusts were
up to 64 km/h whereas temperatures were stable. This deviation
from the protocol was, at the time, not expected to cause any ef-
fect on iodide levels. All other factors including farm management,
milking practices, source of TMR, milkers, and farm staff were
identical for both morning and afternoon milking as well as dur-
ing the execution of the trial. No inconsistencies were identified
during laboratory sample processing or iodide assay, assessed by the
Figure 1–Contribution of iodine teat
disinfectants to milk iodide (µg/L);
0.25 % iodine post-dip, sprayable, or
barrier dip (0.25 DIP; 0.25SP;
0.25BAR); or 0.5 % iodine post-dip
(0.5DIP). Data are calculated relative
to a non-iodine control (CTL) and
corrected for day 0 iodine levels. Data
are presented as LSM ± SEM.
T1868 Journal of Food Science r Vol. 81, Nr. 7, 2016

6. T:Toxicology&
ChemicalFoodSafety
Iodine teat disinfectants and milk iodide levels . . .
Table 5–Milk iodide (µg/L) of selected individual cow milk samples from the control group (CTL) from days −7 to 14 of the
experimental period.
Individual cowsa
Study day 1147 1168 1187 1292 1244
Milk iodide (µg/L)
−7 98 131 174 175 174
0 87 128 142 217 117
1 91 161 159 147 131
10 97 121 161 162 168
14 111 125 173 145 124
a
Individual cows selected from non-iodine control group.
results of the reference sample run with every assay. As no major
inconsistencies were identified throughout the study, the day 14
increase in iodide level may be hypothesized to be the result of
diurnal milk iodide patterns in dairy cattle or may be due to stress
stemming from the impending environmental weather conditions.
In addition, milk iodide in CTL animals significantly increase on
day 14, similar to the cows within iodine treatments. Little data is
available for diurnal or stress related milk iodide patterns in dairy
cattle. However, in humans, it has been demonstrated a circadian
rhythm exists in concentrations of urinary iodine (Als and othes
2000). The same may apply in this study. In addition, Rasmussen
and others (1991) noted daily variations, up to 100 µg/L in milk
iodide, from milk collected during evening milkings when non-
iodine teat disinfectants were used. In that study, the iodine in milk
from cows without the iodine treatment were actually greater than
iodine-dipped animals. In the current study, similar results were
observed on certain study days between the CTL and iodine treat-
ments. The day to day variation that is naturally observed may have
resulted in greater than expected milk iodide.
Milk yield was also decreasing throughout the study as animals
were post-peak in milk and may have influenced milk iodide in
this study. Prior research is mixed if stage of lactation impacts milk
iodine. Previously, milk iodide increased with the stage of lactation
and a negative correlation existed between milk iodide concentra-
tion and total milk yield (Iwarsson 1973; Franke and others 1983).
Another study demonstrated no milk iodine decrease later in lac-
tation (Scherer-Herr, 2001). Although unexpected increases were
observed at day 14, the observed increase in milk iodide levels is
not of great concern for public health as the levels never exceed
maximum recommended level of 500 µg/L. In many countries,
iodine from milk or dairy products is considered an important
component of dietary iodine intake (Andersson and others 2007;
Soriguer and others 2011; Watutantrige and others 2016) and
milk iodine levels reported in this study would also support the
prevention of iodine deficiency.
The method of teat application revealed some differences in
milk iodine levels. Spraying teat disinfectants increased milk io-
dide concentrations by 21 µg/L, an average 13% increase in milk
iodide compared to dipping 0.25DIP following the 23% increase
in 0.25SP consumption (data not shown). The minimal increase
in milk iodide opposes previous research that observed a drastic
122% increase in milk iodine to above 500 µg/L when com-
paring dipping versus spraying with a 1% iodine teat disinfectant
(Borucki Castro and others 2012). The high viscosity barrier treat-
ment (0.25BAR) did not show any dramatic or surprising results
compared with the dip or spray applications. Results for the bar-
rier are consistent with Richard and others (2001). Although it
may still be of important for users to be aware of the difference
of effect on milk iodide between these applications, in the cur-
rent experiment, this difference was small relative to the observed
variation during the trial across different collection days and the
increase does not raise health concerns as long as other sources of
iodine, such as from feed and water, are within the recommended
range.
Conclusions
In conclusion, with the application of iodine based teat disinfec-
tants, a small but statistically significant increase in iodide residue
was observed compared to a non-iodine control disinfectant. Day
to day variation was present but the iodide values remained well
below a predefined WHO safety threshold of 500 µg/L, irrespec-
tive of iodine concentration in the disinfectant and the application
method of the disinfection methods. The potential increases of
iodide concentration in milk due to use of these iodine teat disin-
fectants are likely to be acceptable (within 100 µg/L) when cows
are fed with recommended levels of iodine in their diet and proper
wiping methods are used during the milking procedure.
Acknowledgments
The authors thank the support of the Cobleskill Univ. dairy
farm staff and milkers. The authors also thank the support of
QMPS and AHDC staff. This trial was funded through a grant
from DeLaval to Cornell Univ.
References
Als C, Helbling A, Peter K, Haldimann M, Zimmerli B, Gerber H. 2000. Urinary iodine
concentrations follow a circadian rhythm: a study with 3023 spot urine samples in adults and
children. J Clin Endo Met 85:1367–69.
Andersson M, de Benoist B, Darnton-Hill I, Delange F. 2007. World Health Organization:
iodine deficiency in Europe: a continuing public health problem. France: WHO Library
Cataloguing-in-Publication Data. 86p.
AOAC. 2006. Official methods of analysis. 18th ed. Gaithersberg, Md.: AOAC.
Aumont G. 1987. Milk iodine residues after a post-milking iodophor teat-dipping. Ann Rech
Vet 18:375–8.
Berg JN. 1985. Iodide concentrations in milk from iodophor teat dips. J Dairy Sci 68:457–61.
Borucki Castro SI, Lacasse P, Fouquet A, Beraldin F, Robichaud A, Berthiaume R. 2011. Short
communication: feed iodine concentrations on farms with contrasting levels of iodine in milk.
J Dairy Sci 94:4684–9.
Borucki Castro SI, Berthiaume R, Robichaud A, Lacasse P. 2012. Effects of iodine intake and
teat-dipping practices on milk iodine concentrations in dairy cows. J Dairy Sci 95:213–20.
Borucki Castro SI, Berthiaume R, Laffey P, Fouquet A, Beraldin F, Robichaud A, Lacasse P.
2010. Iodine concentration in milk sampled from Canadian farms. J Food Prot 73:1658–63.
Ceballos-Marquez A, Hemling T, Rauch BJ, Lopez-Benavides M, Schukken YH. 2013. Non-
inferiority trial on the efficacy of premilking teat disinfectant against naturally occurring new
intramammary infections using a novel 2-step diagnostic process. J Dairy Sci 96:8081–92.
Delange F, de Benoist B, Alnwick D. 1999. Risks of iodine-induced hyperthyroidism after
correction of iodine deficiency by iodized salt. Thyroid 9:545–56.
Flachowsky G, Franke K, Meyer U, Leiterer M, Sch¨one F. 2014. Influencing factors on iodine
content of cow milk. Eur J Nutri 53:351–365.
Franke AA, Bruhn JC, Osland RB. 1983. Factors affecting iodine concentration of milk of
individual cows. J Dairy Sci 66:997–1002.
Galton DM, Petersson LG, Merril WG, Bandler DK, Shuster DE. 1984. Effects of premilking
udder preparation on bacterial population, sediment, and iodine residue in milk. J Dairy Sci
67:2580–89.
Galton DM. 2004. Effects of an automatic post-milking teat dipping system on new intramam-
mary infections and iodide in milk. J Dairy Sci 87:225–31.
Iwarsson K. 1973. Rapeseed meal as a protein supplement for dairy cows. I. Influence on certain
blood and milk parameters. Acta Vet Scand 14:570–94.
Vol. 81, Nr. 7, 2016 r Journal of Food Science T1869

7. T:Toxicology&
ChemicalFoodSafety
Iodine teat disinfectants and milk iodide levels . . .
Medici M, Ghassabian A, Visser W, Keizer-Schrama SMPFD, Jaddoe VWV, Visser WE, Hooi-
jkaas H, Hofman A, Steegers EAP, Bongers-Schokking JJ, Ross HA, Tiemeier H, Visser TJ,
de Rijke YB, Peeters RP. 2014. Women with high early pregnancy urinary iodine levels have
an increased risk of hyperthyroid newborns: the population- based Generation R Study. Clin
Endocrinol 80:598–606.
Melichercik J, Szijarto L, Hill AR. 2006. Comparison of ion-specific electrode and high perfor-
mance liquid chromatography methods for the determination of iodide in milk. J Dairy Sci
89:934–7.
Natl. Mastitis Council. 1999. Laboratory handbook on bovine mastitis. Rev. ed. Verona, Wis.:
Natl. Mastitis Council.
Natl. Research Council. 2001. Nutrient requirements of dairy cattle. 7th rev. ed. Washington,
D.C.: Natl Academy Press.
Neijenhuis F, Mein GA, Britt JS, Reinemann DJ, Hillerton JE, Farnsworth R, Baines JR, Hem-
ling T, Ohnstad I, Cook N, Morgan WF, Timms L. 2001. Evaluation of bovine teat condition
in commercial dairy herds: 4. Relationship between teat-end callosity of hyperkeratosis and
mastitis. Proc Int Sym Mastitis and Milk Quality 2:362–66.
Norouzian, MA, Valizadeh R, Azizi F, Hedayati M, Naserian AA, and Shahroodi FE. 2009. The
effect of feeding different levels of potassium iodide on performance, T3 and T4 concentrations
and iodine excretion in holstein dairy cows. J Anim Vet Adv 8:111–14.
Rasmussen MD, Galton DM, Petersson LG. 1991. Effects of premilking teat preparation on
spores of anaerobes, bacteria, and iodine residues in milk. J Dairy Sci 74:2472–8.
Richard JD, Hemling TC, McKinzie MD. 2001. Effects of barrier and high viscosity teat dips
on iodide levels in milk. Proceedings of the Natl. Mastitis Council 40th Annual Meeting,
February 11–14, Reno, Nevada. p. 1–3.
Sanchez LF, Szpunar J. 1999. Speciation analysis for iodine in milk by size-exclusion chromatog-
raphy with inductively coupled plasma mass spectrometric detection (SEC-ICP MS). J Anal
Atom Spectrom 14:1697–702.
Scherer-Herr K. 2001. Iodine excreation via urine and milk in a dairy form in Northrhine-
Westfalia (in German). PhD Thesis.
Scheybal A, Gabrio T, Kirst E, Schmidt KD, Neubert S. 1980. Contamination of milk after post
milking disinfection with iodophors. Nahrung 24:563–67
Shi X, Han C, Li C, Mao J, Wang W, Xie X, Li C, Xu B, Meng T, Du J, Zhang S, Gao Z,
Zhang X, Fan C, Shan Z, Teng W. 2015. Optimal and safe upper limits of iodine intake for
early pregnancy in iodine-sufficient regions: a cross-sectional study of 7190 pregnant women
in China. J Clin Endo and Met 100:1630–8.
Soriguer F, Gutierrez-Repiso C, Gonzalez-Romero S, Olveira G, Garriga MJ, Velasco I, Santi-
ago P, de Escobar GM, Garcia-Fuentes E. et al. 2011. Iodine concenration in cow’s milk and
its relation with urinary iodine concentrations in the population. Clin Nutr 30:44–48.
Sun X, Shan Z, Teng W. 2014. Effects of increased iodine intake on thyroid disorders. Endo
and Met 29:240–7.
Wahlen R, Evans L, Turner J, Hearn R. 2005. The use of collision/reaction cell ICP-MS for
the determination of elements in blood and serum samples. Spectroscopy. 20:84–9.
Watutantrige FS, Cavedon E, Nacamulli D, Pozza D, Ermolao A, Zaccaria M, Girelli ME,
Bertazza L, Barollo S, Mian C. 2016. Iodine status from childhood to adulthood in females
living in North-East Italy: Iodine deficiency is still an issue. Eur J Nutri 55:335–40.
World Health Organization. 2003. Iodine in drinking-water: background document for de-
velopment of WHO guidelines for drinking-water quality. Available from: http://www.
who.int/water_sanitation_health/dwq/chemicals/iodine/en/. Accessed January 25, 2015
World Health Organization. 2004. Iodine status worldwide—WHO global database on iodine
deficiency. Geneva: Dept. of Nutrition for Health and Development.
T1870 Journal of Food Science r Vol. 81, Nr. 7, 2016